Steps to reproduce: 1. Open https://www.instagram.com/nana_eikura/ 2. Key press [End] and then [Home] 3. Optionally, Repeat step 2 Actual Results: Image z-order becomes wrong See attached screenshot

Regression window: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=6415ccbf739f36f71548540bd92c3b86ab9e1529&tochange=d112cf7b2b60e6244099dc3b599a2444ba0d1da3 Suspect: 99de9f5450d8 Matt Woodrow — Bug 1443027 - Fix the merging algorithm to pass the new tests correctly.

Comment on attachment 8980489 [details] Bug 1464288 - Make sure PreProcessDisplayLists logic for switching AGRs matches what ComputeRebuildRegion uses. https://reviewboard.mozilla.org/r/246668/#review252852 LGTM.

Pushed by ryanvm@gmail.com: https://hg.mozilla.org/integration/autoland/rev/5033de939b8c Make sure PreProcessDisplayLists logic for switching AGRs matches what ComputeRebuildRegion uses. r=miko

Backout by ccoroiu@mozilla.com: https://hg.mozilla.org/mozilla-central/rev/52654e368e83 Backed out changeset 5033de939b8c for failing reftests at reftest/tests/layout/reftests/display-list/1464288-1.htm a=backout

Backed out changeset 5033de939b8c (bug 1464288) for failing reftests at reftest/tests/layout/reftests/display-list/1464288-1.htm a=backout Log: https://treeherder.mozilla.org/logviewer.html#?job_id=180267268&repo=autoland&lineNumber=9244 https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/reftest-analyzer.xhtml#logurl=https://queue.taskcluster.net/v1/task/PGYO5FrqRFat8nIZJXOxJg/runs/0/artifacts/public/logs/live_backing.log&only_show_unexpected=1 Push with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&revision=5033de939b8c736d03821284fcdd1fd956ee06b6 Backout: https://hg.mozilla.org/mozilla-central/rev/52654e368e83894860b228e1b08984c27104460a

(In reply to Dorel Luca [:dluca] from comment #8) > Backed out changeset 5033de939b8c (bug 1464288) for failing reftests at > reftest/tests/layout/reftests/display-list/1464288-1.htm a=backout > > Log: > https://treeherder.mozilla.org/logviewer. > html#?job_id=180267268&repo=autoland&lineNumber=9244 > > https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/ > reftest-analyzer.xhtml#logurl=https://queue.taskcluster.net/v1/task/ > PGYO5FrqRFat8nIZJXOxJg/runs/0/artifacts/public/logs/live_backing. > log&only_show_unexpected=1 > > Push with failures: > https://treeherder.mozilla.org/#/ > jobs?repo=autoland&revision=5033de939b8c736d03821284fcdd1fd956ee06b6 > > Backout: > https://hg.mozilla.org/mozilla-central/rev/ > 52654e368e83894860b228e1b08984c27104460a Oh right, linux32 debug has APZ disabled. Forgot to condition the test on that.

Pushed by mwoodrow@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/18a7b3b1332d Make sure PreProcessDisplayLists logic for switching AGRs matches what ComputeRebuildRegion uses. r=miko

Please request Beta approval on this when you get a chance.

Backout by dluca@mozilla.com: https://hg.mozilla.org/mozilla-central/rev/e0beb6560ec9 Backed out changeset 18a7b3b1332d for failing reftests at reftest/tests/layout/reftests/display-list/1464288-1.htm a=backout

Backed out changeset 18a7b3b1332d (bug 1464288) for failing reftests at reftest/tests/layout/reftests/display-list/1464288-1.htm a=backout Log: https://treeherder.mozilla.org/logviewer.html#?job_id=180344204&repo=autoland&lineNumber=10327 Push with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&revision=18a7b3b1332df10c4b6755279dc0200f524c3e3e Backout: https://hg.mozilla.org/integration/autoland/rev/e0beb6560ec9a46029018ef9992795f1607dc410

Pushed by mwoodrow@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/4fe333a81f25 Make sure PreProcessDisplayLists logic for switching AGRs matches what ComputeRebuildRegion uses. r=miko

Comment on attachment 8980489 [details] Bug 1464288 - Make sure PreProcessDisplayLists logic for switching AGRs matches what ComputeRebuildRegion uses. Approval Request Comment [Feature/Bug causing the regression]: Retained-dl [User impact if declined]: Incorrect z-order sorting in some situations. Affect instagram, while logged out (at minimum). [Is this code covered by automated tests?]: Yes, new reftest added. [Has the fix been verified in Nightly?]: Yes. [Needs manual test from QE? If yes, steps to reproduce]: No. [List of other uplifts needed for the feature/fix]: None. [Is the change risky?]: No. [Why is the change risky/not risky?]: Just increases the number of items we mark to account for async scrolling, no new code paths. [String changes made/needed]: None.

Comment on attachment 8980489 [details] Bug 1464288 - Make sure PreProcessDisplayLists logic for switching AGRs matches what ComputeRebuildRegion uses. RDL correctness fix with a new reftest included. Approved for 61.0b9.

I’ve tried to observe this issue on several platforms/test machines on the affected Nightly and Beta (included with japanese builds), but unfortunately, I couldn't reproduce its behavior. Alice, can you please, verify if this is still reproducible on your side, on the fixed Firefox builds? Thank you!

I can manage to reproduce the issue on Win10 x64 Nightly62.0a1(build ID 20180525005138) and 61.0b8(build ID 20180524181234). And I verified to fix on Win10 x64 Nightly62.0a1(build ID 20180528220216) and 61.0b9(build ID 20180528091514).